Counting, direct-converting x-ray detectors can be used in x-ray imaging, for example in computed tomography, angiography or radiography. The x-ray radiation or the photons can be converted into electrical pulses by a suitable sensor. Counting x-ray detectors make it possible, as well as counting events, also to provide information about the energy of the detected x-ray quantum. New opportunities are thus opened up in medical imaging for the analysis and evaluation of the signal.
CdTe, CZT, CdZnTeSe, CdTeSe, CdMnTe, InP, TlBr2, HgI2, GaAs or other materials can be used as converter material for the converter element for the sensor for example. The energy of the incident ionizing radiation is converted directly into electrical charges, so-called electron-hole pairs. A high voltage, for example for CdTe, CZT, CdZnTeSe, CdTeSe or CdMnTe in the range of −500 to −2000V, is applied to the converter element between an electrode as cathode and a readout contact as anode, in order to separate the charges of the electron-hole pairs released in the converter element. The high voltage is applied to the electrode via an external high-voltage source by way of an electrically-conductive contact. As a rule the sensor is connected in a planar manner in a stack arrangement to a readout unit and/or an evaluation unit, for example an integrated circuit (Application Specific Integrated Circuit, ASIC), via solder connections, electrically-conductive adhesive or other methods. The electrical pulses are evaluated by an evaluation unit, for example by an ASIC. The stack arrangement having the sensor and the integrated circuit is connected to a further substrate, for example a circuit board, a ceramic substrate such as HTCC or LTCC or others for example. The electrical connections for reading out the readout and/or the evaluation unit can be embodied by way of through silicon vias (TSV) or wire bonds.
A direct-converting x-ray radiation detector, which has at least one electrode attached to a semiconductor, is known from DE 10 2012 213 410 B3. The at least one electrode and the semiconductor are connected electrically-conductively, wherein the at least one electrode is embodied transparent and electrically-conductive. In order to optimize the x-ray radiation detection it is known to irradiate the semiconductor used for detection with an additional radiation for creating additional charge carriers. IR, UV or visible radiation is used as additional radiation for example.
The trend to larger detector facilities, especially to larger z extents, and the simultaneous cost competition with established detector technologies, for example indirect converting detectors, present the development of detector apparatuses with new challenges.